Activists from Unite, Britain’s biggest union, and NIPSA, which represents thousands of public sector workers in Northern Ireland, said measures had been put in place to prevent demonstrations in Belfast and Fermanagh being hijacked by troublemakers.

“If you are intent on trouble do not come near our demonstration. We won’t allow this demonstration to be hijacked,” said Gary Mulcahy, a spokesman and co-ordinator for the G8 Not Welcome campaign.

Thousands more are expected to travel west for another rally against the G8 summit in Enniskillen on Monday.

Protesters will attempt to get as close to the world’s eight most powerful leaders as possible by snaking their way on a pre-agreed route through the town towards a perimeter fence erected around the site of the luxurious Lough Erne resort. The protest is expected to last for up to four hours.

The trade unions have also accused the Government of scaremongering in an attempt to put people off joining protests.

Jimmy Kelly, Unite regional secretary, said an atmosphere of fear was being deliberately stirred up ahead of the conference.

“All the build up is designed to put people off with wall-to-wall police, back up and drones and everything you can think of.

“We are trying to cut through that intimidation climate to say you are entitled to protest, be proud to protest because our aims are just and we are a force for good. If you want to go out with your family and be part of the protest you are concerned that the security is going to go over the top.”

“Trade unionists who will protest against the G8 in Belfast and Fermanagh have warned violent anti-capitalist thugs not to hijack their demonstrations.”

There’s another potential source of violence in these types of protests than just “anti-capitalist thugs.” Some of the larger 2011 Occupy demonstrations in the U.S. were infiltrated by so-called “agent provocateurs.” They were undercover law enforcement personnel, and possibly others with ties to the financial industry or the federal government, who stirred up trouble in order to discredit the Occupy movement in the eyes of the public.

This is a very old tactic which labor organizations should be familiar with since it has been used against them on countless occasions dating back to the earliest days of the labor movement.